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https://issues.apache.org/jira/browse/HDFS-12996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16324775#comment-16324775
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Hanisha Koneru commented on HDFS-12996:
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Thanks [~virajith] for the review.
bq. In Section 13, Step 5, which component receives the restore-replica-trash
command? From my understanding this should be the Namenode. However, in step 5
the Namenode is not running. How is this going to work?
You are right. The Namenode would first need to be restarted and then the
restore-replica-trash command needs to be issued. Steps 5 and 6 got
interchanged. Will fix this in the next version of the document. Thanks for
catching this.
bq. Have you looked at "undoing" the delete operation? I think this would need
to handle conflicts (for example, /foo/bar was deleted but a new /foo/bar/ is
created) but could avoid having to stop and restart the Namenode.
Our current proposal handles a simpler use case of recovery via rolling back
everything to an earlier point in time. Something similar to what you proposed
could be built on top of the replica trash though.
bq. Can the replica purge daemon functionality be implemented in the
VolumeScanner?
Yes that may be possible. We will look into it when we get to the purge
implementation.
> DataNode Replica Trash
> ----------------------
>
> Key: HDFS-12996
> URL: https://issues.apache.org/jira/browse/HDFS-12996
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Hanisha Koneru
> Assignee: Hanisha Koneru
> Attachments: DataNode_Replica_Trash_Design_Doc.pdf
>
>
> DataNode Replica Trash will allow administrators to recover from a recent
> delete request that resulted in catastrophic loss of user data. This is
> achieved by placing all invalidated blocks in a replica trash on the datanode
> before completely purging them from the system. The design doc is attached
> here.
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